Correlation of Stage of Keratoconus and Corneal Endothelial Count and Morphology: Specular Microscopic Study
Narrative Responses:
Purpose
To study the corneal endothelial count and morphology in keratoconus patients by specular microscopy, and correlate them to the stage of keratoconus.
Methods
Forty eyes of 29 keratoconus patients were enrolled in this cross-sectional cohort study. Corneal endothelium was evaluated using specular microscopy, and corneal topography and thickness data were obtained from Scheimpflug-based corneal tomography. Eyes were classified according to thinnest corneal thickness (TCT) into 2 subgroups, group A, with TCT ≤ the cohort median (400µ), and group B, with TCT > 400µ. Eyes were also classified into stages 1, 2 and 3 of keratoconus according to Amsler’s classification, utilizing keratometry and pachymetry readings obtained from corneal tomography.
Results
Endothelial cell density was lower in group A than group B (2327 ±621 cells/mm2 vs. 2411 ±334 cells/mm2, p=0.59), as was the coefficient of variation (34.7 ±10.0 vs. 36.4 ±8.0, p=0.55). The percentage of hexagonality was higher in group A (60.9 ±12.2% vs. 57.3 ±13.8%, p=0.41). Eleven eyes (27.5%) had stage 1, 17 eyes (42.5%) had stage 2, and 12 eyes (30%) had stage 3. Specular microscopy was not possible in stage 4. There was no correlation between stage of keratoconus and endothelial cell density (r=0.018, p=0.91), coefficient of variation (r=-0.011, p=0.94), or percentage of hexagonality (r=-0.112, p=0.51).
Conclusion
Up to stage 3, keratoconus does not significantly affect the corneal endothelium, as measured by specular microscopy. Eyes with stage 4 could not be studied by specular microscopy, and may require other imaging methods such as confocal microscopy.